1. Field of the Invention
The present invention relates to a combustor and a method for modifying the same.
2. Description of the Related Art
Power-generating plants that support industrial electric power services include gas turbine power-generating plants fueled by a natural gas, petroleum, or other fossil resources. Since the gas turbine power-generating plants fueled by fossil resources release the carbon dioxide (CO2) that is a global warming material, these power plants are being required to improve power-generating efficiency more significantly than ever before. Ways to improve power-generating efficiency include increasing the temperature of the combustion gases released from the gas turbine combustor. However, as the combustion gas temperature is increased, nitrogen oxides (NOx) that are an environmental pollutant contained in the combustion gases will increase exponentially. It is therefore becoming a technically crucial challenge how to reduce NOx while enhancing power-generating efficiency.
Operational cases of the gas turbine power-generating plants powered by a hydrogen-containing fuel such as the coke-oven gas occurring in a coke oven during iron-and-steel making processes are also increasing in recent years from the perspective of global-warming prevention and control. In addition to the coke-oven gas, examples of hydrogen-containing fuels include a by-product gas called the blow-off gas occurring in an oil purification process, and a coal gasification gas that is used at integrated gasification combined cycle (IGCC) power-generating plants. Because of its wide combustible range and its high combustion rate, the hydrogen contained in the fuel may form high-temperature flames near the walls of the combustor, deteriorating combustor reliability. In order to prevent local formation of high-temperature flames, it is effective to disperse the fuel and burn the fuel uniformly in the entire combustor.
JP-2003-148734-A, therefore, discloses a technique for disposing an air blowhole plate between a fueling nozzle and combustion chamber in a combustor, forming a fuel flow and an air flow at the outer circumferential side of the fuel flow, inside air blowholes provided in the air blowhole plate, and jetting the fuel flow and the air flow into the combustion chamber. The combustor described in JP-2003-148734-A is constructed so that NOx can be reduced by enhancing dispersibility of the fuel with respect to the air.